Accurizing and Dwell Time

[rodauto]

Paul.....
Youre making me crazy with all these modifications!! I haven't even been able to play for weeks and you have been having all these adventures.
I think if youre dwell is around .010 youre pretty good according to many of the threads I have followed in the last year or so, time to try and fine tune the loads again? Did the unitized gas cylinder reduce the stringing at all?
Rodney

 

[Pr589]

Paul.....
Youre making me crazy with all these modifications!! I haven't even been able to play for weeks and you have been having all these adventures.
I think if youre dwell is around .010 youre pretty good according to many of the threads I have followed in the last year or so, time to try and fine tune the loads again? Did the unitized gas cylinder reduce the stringing at all?
Rodney

Rodney - Too early to tell about the stringing given op. rod collisions with the gas cylinder and perhaps a need to adjust the load. Had a good run of about 50 rounds then things went south. I would be ok with a dwell of 0.10 but 0.12 makes me wonder if correcting this would Improve things.

 

[rodauto]

Rodney - Too early to tell about the stringing given op. rod collisions with the gas cylinder and perhaps a need to adjust the load. Had a good run of about 50 rounds then things went south. I would be ok with a dwell of 0.10 but 0.12 makes me wonder if correcting this would Improve things.

.002 off the piston is likely 2 strokes with a fine file... go slow can'tput the metal back!!!

 

[Pr589]

.002 off the piston is likely 2 strokes with a fine file... go slow can'tput the metal back!!!

Typo...the recommended dwell is 0.01" not 0.1", so I'd have to remove a fair amount. I tried with a fine file on the tail of the piston but it's slow going. May try my Dremel later.

 

[gnmontey]

Originally Posted by jonh172
you don't want the oprod making hard contact on the bolt roller when in battery



With your action locked up in battery, loosen your gas plug, your oprod should move ever so slightly forward.
You can also use a very fine pin punch or something similar to try to roll the roller while in battery, if either method won't move the respective part, then you may have an issue.

Can spin mine using a taxidermy pin no problem, so I guess I'm GTG!

Thanks,

M

 

[jonh172]

Typo...the recommended dwell is 0.01" not 0.1", so I'd have to remove a fair amount. I tried with a fine file on the tail of the piston but it's slow going. May try my Dremel later.

Try making a washer with shim stock and shim your gas plug, if it solves the problem then remove the material off of the piston, if it makes no difference then save yourself the hassle and look elsewhere for the issue.
I doubt 0.002" Is going to make a huge difference.

 

[jonh172]

Shimming the gas plug will actually increase dwell time also.
Dwell time is the time before the piston starts to move, so trimming the tail doesn't actually increase this time; it increases the time before the bolt unlocks. So you may still have stringing as your oprod will start moving at the same time.
If you want to slow down the time it takes before oprod starts moving, you need to increase cylinder volume.
The gas cylinder is like a balloon, dwell time is the time it takes to blow up the balloon; shimming the gas plug increases the balloon volume; or modifying the internal spec of the plug increases the volume of the cylinder.
Don't shim too far though, you don't want to cut off the gas travelling into the cylinder all together, and shimming is not the fix; just a test; don't leave the shims in permanently.

 

[TonyBen]

I try to just set my rifle to require 1.5 turns of the gas plug to reach snug from the time the piston makes contact with the operating rod. You can go longer or shorter but 1.5 turns is a good starting point.

Tony.